1. Field of the Invention
The present invention is related to the field of electronic devices. In particular, the present invention is related to a method and apparatus for supplying power to electronic circuits.
2. Description of the Related Art
Power supplies generate power and maintain a relatively constant voltage and current for circuits of an electronic system. Power supplies generally convert an alternating current (AC) input voltage into a regulated direct current (DC) output voltage. In instances where the power supply input voltage is a DC voltage, the power supply may be a DC-DC converter such as a linear or a switching voltage regulator. A load line of a power supply may be defined as a line that represents the load current for different values of load voltages.
FIG. 1 illustrates a conventional a power supply load line. As illustrated in FIG. 1, the conventional power supply load line 108 represents the voltage and current values of a load (i.e., an electronic circuit) between a no load condition (zero load current) and a full load condition (maximum load current). At 110, the no load condition, when the load current is zero the load voltage is maximum; and at 112, the full load condition, when the load current is maximum the load voltage is minimum. Between the no load condition and the full load condition the conventional load line is substantially linear, indicating that the voltage and currents output by a voltage regulator between these two points is linear. As illustrated in FIG. 1, the load line 108 is shifted by a certain margin below line 106. Line 106 is the rel-line (reliability-line), and the margin by which the load line is shifted is approximately equal to the voltage drops produced by the voltage regulator control tolerance, the DC drop (the voltage drop due to the DC components of the load), and the AC drop (the voltage drop due to AC components of the load). The rel-line 106 represents the maximum voltage a circuit may be exposed to for a given value of current. Operating a load at a margin below the rel-line prevents the load from being damaged in the event of a voltage overshoot.
Successive generations of microprocessors operate at increasing frequencies and consume increasing amounts of currents. These operating frequencies are much greater than the switching frequencies of the voltage regulators employed in the power supplies that supply power to the microprocessors. Therefore, the power supplies' decoupling capacitors supply charge to the microprocessors until the voltage regulator of the power supply can respond to the current demands of the microprocessor. This means that for successive generations of microprocessors to operate properly, the voltage regulator's decoupling capacitance may be increased, the voltage regulators may switch at higher frequencies, the interconnect resistance of the circuits may have to be reduced, etc. The net result of implementing these solutions is that system impedance (i.e., the impedance of the load) is reduced and the cost of supplying power increases. Therefore, these solutions for supplying power to a load are undesirable.